Re: [PPPRS] Safety cut-off switch

[Ray Scheufler]

https://www.pegasusautoracing.com/productdetails.asp?RecID=1465
This is used in real race cars.

There is always the anderson power pole connector option. It may wear
out over time but it could be could be replaced easily. Have a
standard paint option on the loop so marshals can easily find it.

Ray Scheufler

On Sat, Nov 10, 2012 at 3:04 PM, Micah Erickson
<erickso...@gmail.com> wrote:
> http://autoplicity.com/products/431737-longacre_racing_products_45780_longacre_battery_disc_sw_w_o_panel_4trm__altn__75_1000a.aspx?utm_source=GoogleShopping&utm_medium=CSE&utm_content=431737NOFITMENT&utm_campaign=GSNOFITMENT
>
> Does physical cut-off, should be externally mounted
>
> $27, $32shipped

[T Davis]

http://www.robotmarketplace.com/products/0-SWHELLA1.html

[Jon Halverson]

http://www.evdrives.com/product_p/sol-ed250.htm

[jesse]

we tried regular racing cut offs but they are not made for 36v. we are 2 for 2 on failures of racing cut-off switches. they work fine in my 5.0 mustang but then again I'm not using the starter motor to move the car. :)

[Jon Halverson]

Its important for a safety switch in our application to be able to break the potentially high currents we're dealing with here.  In a race car the safety switch is needed to cut power to the spark plugs.  That is a lot less current then we're dealing with.

For those without an electrical background:
You can think of current traveling in an inductor (battery cables) as having a certain amount of momentum.  When you open a switch while that current is flowing it does not want to just stop immediately. The voltage will rise at the junction to try to maintain the path with an arc.  This arc can cause the switch to weld itself shut. It can also cause oxides to build up on the contact surface which increases the contact resistance which causes local heating and eventually melting. (this actually happened to the fan switch on my 92 Merc Topaz) The more current you want to break, and the higher the voltage, the harder it is to design a switch.

To see this effect in large scale:
http://www.youtube.com/watch?v=hIkNY5xjy5k
The arcing is part of proper switch behavior here.

This video also provides us with a lesson we should learn from:
http://www.youtube.com/watch?v=N8fwtkC5UJU&feature=fvwrel

[Tom Gralewicz]

What I have been using on LPT and Jake are commercial contactors designed to switch high currents:

https://www.surpluscenter.com/item.asp?item=11-3278&catname=electric

(Make sure you get the continuous duty versions)

and a 12V circuit controlling it.  I use Anderson 30A connectors on a pig tail with a loop as the kill switch.  We have not had problems with unplanned disconnects but it kills the power if you give a hank on the connector.

http://www.powerwerx.com/anderson-powerpoles/powerpole-sets/15-amp-red-black-anderson-powerpole-sets.html

(I have a few hundred of these in a lovely blue that I could donate to the cause)

The alternative is to use a main fuse and a shorting block to blow the fuse as an emergency shut off.

P.S.  Fuses should me a mandatory safety system, both on the main motor power and on any low current circuits.

--
Tom Gralewicz
Miller Electronics Recycling
(414) 380-1716
www.deadcomputers.com

[Eli Richter]

I like the switch Jon suggested.  According to the documentation on the company's website (here), it can break the connection at full rated current and is rated to 48VDC.  Assuming we decide on this switch, the question is, do we specify this as a minimum and allow commercially available equivalent, so long as it is specifically rated to break the circuit at full current (and must be pre-approved by sending documentation x weeks prior to the event), or do we just say this is the only option?

-Eli

[Joe Kerman]

That is a fantastic switch, at a fantastic price. I would vote for
making one particular model of switch standard. It would give us an
advantage in that any track Marshall or any member of any team, could
know how to turn off any car on the field in an emergency.

Perhaps any switch in that product line, with that current rating "or
better". The key switch models, and models with optional coils are
very nice.

Another note is that this switch is rated only as an emergency
disconnect, and it is not designed for repeated use at high current.
i.e. no using this switch as your gas pedal :) (and yes, we should
probably make that a rule!)

[Bill French]

I'd like to +1 the anderson connector with a loop.  They sell red handles, too, for example:

http://www.powerwerx.com/powerpole-accessories/995G2-995G4-sb350-handle-kit.html

I think i noticed nearly everyone at NYC was using some form of anderson connectors for their batteries, so this is just adding one more set mounted in a conspicuous location with an obvious red handle of some sort.

No doubt it can handle the load, and worrying about it wearing out seems a bit unrealistic to me.  (since they are already being used)  They are simple to understand, inspect, and service.

You can see ours mounted in the center of this photo:

[Eli Richter]

Bill,

We also currently use the Anderson power pull for a disconnect.  There are two problems with this solution though for which I'd recommend using a switch. 

The first is that each time we plugged in our connector (we used it also as our "key" to safe the car), there was a small spark, which over time caused enough degradation of the contacts to the point that the plug became hard to pull. This may be a fixable problem, but at a minimum it would have to be addressed.

The second and I think bigger issue is that it's much harder in an emergency to grab a handle and pull versus smack a big button.  For this reason I think that we should go with a button of some kind, even though it's a slightly more expensive option (though really, $25 should not break the bank for anyone).

I would +1 at least making the product family standard, since as Joe said, some teams might want to opt for additional options on the switch.

[David M. N. Bryan]

Hey folks,

How many times have we actually had use one of these?

Did it fail in stopping the car?

If it ain't broke, why fix it? 

The first year we used a zip tie electrical taped to a spade connector.  The less requirements, the better chance people have at participating.

-David
Hack Factory

---

[T Davis]

i think the point to this is running the race in off does not work.

[Joe Kerman]

In detroit, when sector67's motor controller had a fault that set the
throttle to max instead of 0 when the throttle cable got accidentally
cut. it was only the E-stop that saved the car from pushing through
the barriers and going off into the crowd at 25mph. I was able to dive
into the car and disable it in 1 second. The main point is that *any*
person on the track, from any team, or any track Marshall can disable
any car instantly without thinking.

Its also just a plain old sane safe idea whenever you have an
electrical circuit dealing with dozens of amps. So everyone /should/
for sanity reasons have one already. Everyone using the same one just
takes something everyone already (should) have, and makes it more
accessible.


P.S. My sister lives about 1 mile away from hack factory, I stopped by
the weekend before thanksgiving in a huge rush, and was able to get a
5 minute whirlwind tour of the space. I left a little acrylic state of
WI on top of your thermostat. :) You guys have a really really amazing
space over there! I hope I get some time to come and hang out for a
little bit longer sometime soon. I especially liked the vending
machines, and your "parking ticket" system of organizing stuff.

[Pete Prodoehl]

I approve of Joe's message.

And agree with it.

etc.


Pete

[jesse]

So I found this on Makeitlabs site and i got in touch with Max and he said its open to all. any interest? we have to get a video back by Monday.

Bray Entertainment, the Co-Creators of Pawn Stars, is casting and developing a new show with the working title American Makers about specialized building and mechanics. We are looking for three to five groups of makers to compete every episode to create the best version of a proposed project. Whether it's a robotic refrigerator, giant laser or automatic pumpkin carver, we want to highlight the process of making along with the colorful characters that create the projects themselves.

If you would like to get started right away on a casting video, here are the instructions below ---

Website to submit a casting video  -   https://www.wetransfer.com/

Step 1: Add file - add your video 

Step 2: Enter one of these email addresses - maxwell@brayentertainment.com

Step 3: Enter your email Address 

Step 4: Type your message - Tell us your location, your name, and your company's name

Step 5: Click Transfer

Another option for submitting a video is to shoot it and then upload it to YouTube. Just make sure you upload it as unlisted and send me the link.

Please answer these questions in the video -

What is your full name?

How old are you?

How long have you been building specialized items?

What is you favorite thing about it?

What is your least favorite thing?

What is your best creation?

Do you have any interesting stories?

Tell us a little bit about yourself and the people you work with! Be creative, show us a lot of energy and most importantly HAVE FUN!

Some Do's and Don'ts of making a video: 

- Please have someone else hold the camera for you. Do not hold the camera yourself.

- If you are filming with an iphone, film with the phone horizontally. 

- Make sure to film in a well lit area
- Please do not film with any music or edit with any music

- Also, stand-up in the video. When you sit, the shot can look static and uneventful.

  

Please only send us files in .mov or .mp4  

The video file can be no larger than 2 GB to fit on wetransfer

We can not view your video otherwise. If this is a problem, please call me/email and let me know.

Please submit video by Monday Dec 17th noon EST.

Cheers,

Max

-- 

Maxwell Lloyd

Bray Entertainment

80 River Street Suite 5D
Hoboken, NJ   07030

p: 212 993 8509x8509

c: 561 352 5622
e: maxwell@brayentertainment.com
w: brayentertainment.com

t: @bray_ent